Cartesian robots, as manufactured, typically have three primary sources of correctable error in their movement to target locations. The first is an offset error, a displacement in X or Y that does not vary over the area of the bed. The second error component is scale inaccuracy, where a commanded movement systematically results in more or less movement than requested. The third source of error is skew, when a requested movement in X creates an unintended movement in Y, or a requested movement in Y creates an unintended movement in X.
These three errors, offset, scale inaccuracy, and skew are machine specific errors and cannot be preset for all robots manufactured. For each machine manufactured, each of the errors must be determined and correction factors set. The correction factors must also be redetermined and reset occasionally due to a number of events including routine operation, the machine being moved or bumped, or as part of a regular maintenance schedule.
Because of the need to set the correction factors for each machine, a simple and reliable alignment correction system and method of determining those factors is desirable. We hereby provide such a system and method.